Based on the above data, a mix of 3 odds and 3 evens are okay, as well as the ratio of 2 odds and 4 evens, or 4 odds and 2 evens. However, you cannot put aside that from time to time, a ratio of 1:5 or 5:1, though rarely, can also become true.
If you want to cover all probable ratios except the 0:6 and 6:0 ratios, you can play 9 lines (9 combinations) where 3 of them have the 3:3 odd-even ratio (see the column To Play). Depending on your budget, you may play fewer lines.
Where do you position the odd and even numbers? Based on probability data, the position of the odd and even numbers are not that significant. The variance between one odd-even pattern to another is very low. If you want specific odd-even patterns to combine numbers, you may download my LG+ from this page.
Here's another way to play lotto!